甘肃礼县河西沟金矿成矿地质条件对比分析

GEOLOGICAL CONDITIONS AND PROSPECTING DIRECTION OF HEXIGOU GOLD DEPOSITS IN LI COUNTY,GANSU PROVINCE

甘肃礼县河西沟金矿地处西秦岭造山带礼岷金成矿带东南段中川岩体周缘,目前发现的矿体主要产于中泥盆统舒家坝群碎屑岩组和上石炭统东扎口组中,属于NW(W)向—NE向叠加构造带内的构造蚀变岩(微细粒浸染)型金矿。研究发现,矿体受地层与岩浆岩的热接触变质带和构造破碎蚀变带的共同控制,构造破碎蚀变带为成矿热液的运移提供了通道和沉淀的场所;成矿作用以中川岩体的岩浆活动为重要的成矿热动力源,以黄铁矿化为重要的找矿标志,且具有多期次成矿的特点,容易在褶皱核部形成矿体富集。地球物理和地球化学异常与矿化蚀变带及含矿层位有较好的套合指示。本文结合本矿区的地质特征,分析对比成矿条件,提出找矿方向,为西秦岭地区的构造蚀变岩(微细粒浸染)型金矿床勘查工作提供参考。

Hexigou gold deposits is located in the southeastern Lixian-Minxian gold metallogenic belt of West Qinling orogenic belt in Gansu province.Presently discovered ore bodies are Liba micro-fine granular disseminated-type ore in hydrothermal alteration mineralized zone controled by fault zone which controlled by northwest(NW)and northeast(NE)fault zone,mainly occurs in the hornfels and slate of Middle Devonian Shujiaba formation and Upper Carboniferous Dongzhakou formation.The research reveals that the main ore bodies are controlled by contacting zone between stratum and irruptive Zhongchuan rocks and the fracture structural alteration zone,meanwhile,ore can be strongly enriched in the core of folds(especially anticline),Pyrite mineralization could be the important clue on prospecting.The structural fracture alteration zone provides a channel and a place for the migration and precipitation of the ore-forming hydrothermal fluid.The magmatic activity of Zhongchuan rock body is an important source of ore-forming thermal power,and the pyritization is an important prospecting indicator.Comprehensively compare with the same type deposits in the district,it can be found that the studied deposit is related to multiple magmatic pulses including the early period of a certain magmatic affair as the main metallogenic period.Besides,geophysical and geochemical anomalies are well correlated with mineralized alteration zones and ore bearing horizons.This assay will combine the same type of deposits in the district and tectonic,geological settings,discuss the ore-prospecting orientation,predict ore potential and offer elicitation for exploration of other structural altered rock(micro particle disseminated)type gold deposits in West Qinling area.